Iron Formation in Neoarchean Deltaic Successions and the Microbially Mediated Deposition of Transgressive Systems Tracts
Bibliographic record
Abstract
Abstract Neoarchean deltaic deposits present in Superior Province, Canada, contain an excellent record of shallow-water siliciclastic and iron formation (IF) deposition. The deltas were fed by braided fluvial systems, which commonly resulted in the development of small, active lobes that repeatedly cycled through progradation and abandonment, although a thick progradational deltaic assemblage was also investigated. Magnetite-rich chemical sediments interbedded with siltstones and slates are present on flooding surfaces overlying shore-proximal fluvial channels and distributary-mouth bars of the braid-delta deposits. Magnetite laminae are also interbedded with some distributary-mouth sediments draping reactivation surfaces in ripples to barforms. Thicker accumulations of IF (up to 73 m) form portions of transgressive systems tracts where chemical sedimentation dominated. Offshore equivalents of these successions do not contain chemical sediments. Sedimentologic data imply that IF deposition in this well-mixed, nearshore water mass was not compatible with slow rates of constant iron-compound precipitation in the world ocean combined with siliciclastic sediment starvation. The model presented for iron precipitation relies on an elevated flux of continentally derived nutrients in the nearshore, stimulating photosynthetically induced oxidation of Fe2+. Under these conditions, elevated accumulation rates precluded the development of condensed intervals characteristic of transgressive systems tracts.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".